Interface demon

Interface to the DFT program deMon (academic license free of charge). DeMon uses advanced density fitting techniques enabling very efficient calculations.

The interface supports also the development version of deMon implementing constrained DFT (cDFT) methodology.


The default auxiliary basis for density fitting in deMon is rather small. To achieve absolute energies comparable with other DFT programs, it must be increased to GEN-A3* or better.

Methods and capabilities

The interface implements following methods (specified by keyword 'method'):

The interface implements following atomic charge types (keyword 'atomic_charges'):

Input structure

Optionally, following blocks can be defined in the input:

Keywords used

Keywords specific for this interface:

Other keywords used by this interface:


The following examples, along with all other files needed to run them, can be found in the directory cuby4/interfaces/demon/examples

# deMOn interface example 1: configuration and simple calculation

# Energy of water molecule
job: energy
geometry: A24:water
charge: 0

interface: demon
method: dft

# DFT setup
basisset: DZVP
functional: b-lyp # the name of the functional is translated to deMon's format

# Interface configuration
# The following keywords configure the interface. These values have to be
# adjusted for a particular installation of deMon. To reuse the configuration,
# put it into the config file.

# Path to deMon exacutable
demon_exe: /home/rezac/bin/demon/2.5.4/demon_cdft_200613/deMon.2.5.4.opt
# Path for loading libraries (optional, added to LD_LIBRARY_PATH)
demon_lib_dir: /home/rezac/bin/demon/4.2.4_master_bin/libs

# Version - needed for generation of correct input for given version
demon_version: "2.5.4"

# A development version of deMon has an option enabling additional data
# being passed to Cuby
demon_with_cuby_interface: yes

# Paths to deMon's data files 
demon_basis_file: /home/rezac/bin/demon/2.5.4/deMon/BASIS
demon_auxis_file: /home/rezac/bin/demon/2.5.4/deMon/AUXIS
demon_ecps_file: /home/rezac/bin/demon/2.5.4/deMon/ECPS
demon_mcps_file: /home/rezac/bin/demon/2.5.4/deMon/MCPS